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Propamocarb

Publication Date: 10/97

TRADE OR OTHER NAMES

The active ingredient propamocarb hydrochloride is considered a carbamate fungicide, however, it is not a methyl carbamate anddoes not inhibit cholinesterase. Some trade names for products containing propamocarb include Banol, Prevex, Previcur, Tattoo C, Tattoo M, Dynone, Filex, and Proplant. Formulations come as an aqueous concentrate (1, 2, 3, 6).

REGULATORY STATUS

Propamocarb is a registered active ingredient with the U.S. Environmental Protection Agency (EPA), which has been undergoing reregistration. Propamocarb is currently registered by EPA for non-food uses on turf and ornamentals as Banol (2). Outside the U.S., the active ingredient is used on tobacco, vegetables, strawberries, potatoes and other crops. Propamocarb is considered a general use pesticide with a toxicity classification of IV (relatively non-toxic). Check with specific state regulations for local restrictions which may apply. Products containing propamocarb must bear the signal word "Caution" on their label (3).

INTRODUCTION

Propamocarb is a specific fungicide with specific activity against several Oomycete species which cause seed, seedling, root and stem rots and foliar diseases in many edible crops and ornamental plants. The mode of of action is different compared to other Oomycete fungicides, which provides for efficacy against strains that have developed resistance to other fungicides. Crops include potatoes, turf, and ornamentals (1, 2).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

There are no acute toxicity concerns with propamocarb. The acute rat oral LD50 was 2,900 mg/kg in males and 2,000 mg/kg in females. The acute rat dermal LD50 was less than or equal to 3,000 mg/kg. The acute (4-hour) inhalation LC50 in rats was >7.9 mg/l. Propamocarb was not a skin sensitizer in guinea pigs. Based on these results, propamocarb hydrochloride was classified as Toxicity Category III for acute oral and dermal toxicity, and eye irritation, and Category IV for acute inhalation toxicity and skin irritation (4).

CHRONIC TOXICITY

In a 90-day feeding study, propamocarb was administered to albino rats at concentrations of 0, 20, 50, 100, and 500/1,000 ppm in the diet. The only effects noted were slightly reduced food efficiency and body weight gains at 1,000 ppm (4).

In a 90-day feeding study in beagle dogs, propamocarb was administered in the diet at concentrations of 0, 50, 100, 500, and 1,000/2,000 ppm. No treatment-related findings were observed (4).

A 21-day dermal toxicity study was performed with propamocarb in Sprague- Dawley rats at dose levels of 0, 100, 500 and 1,000 mg/kg/day, 6 hours per day, 5 days per week over a 21-day period. No treatment related effects were observed (4).

A 21-day dermal toxicity study was performed with propamocarb in rabbits at dose levels of 0, 150, 525 and 1,500 mg/kg/day, 6 hours per day, 5 days per week, over a 21-day period. The No-Observed-Effects-Level (NOEL) for this study was considered by the Agency to be 150 mg/kg/day based on dose-related skin irritation in mid- and high-dose animals and a decrease in weight gain in mid-dose females (4).

A 2-year feeding chronic toxicity/carcinogenicity study was performed in Sprague-Dawley rats with propamocarb at dietary concentrations of 0, 40, 200 or 1,000 ppm. There was no evidence of carcinogenicity or other treatment-related effect except for a possible reduction in food intake in female rats at the highest level tested. Thus, 1,000 ppm (41 mg/kg/day) was considered to be the NOEL (4).

A 2-year feeding chronic toxicity/carcinogenicity study was performed in CD-1 mice with propamocarb at dietary concentrations of 0, 20, 100 and 500 ppm. No evidence of carcinogenicity or toxicity was noted at any dose level. Thus, 500 ppm (53 mg/kg/day for males and females, respectively) was considered to be the NOEL (4, 6).

A 2-year feeding study was performed in beagle dogs with propamocarb at dietary concentrations of 0, 1,000, 3,000, 10,000 ppm. Decreased weight gain, decreased food efficiency and an increased incidence of acute gastric mucosal erosions and/or chronic erosive gastritis were noted in all treated groups. Thus, a NOEL for this study was not determined but was considered to be slightly lower than the lowest dose level tested (33.3 mg/kg/day) (4).

Reproductive Effects

In an investigation on rats over three generations, propamocarb hydrochloride caused no effects at concentrations up to 1000 ppm (1).

In a developmental toxicity study, rats were administered propamocarb by gavage at dose levels of 0, 74, 221, 740, or 2,210 mg/kg/day on gestation days 6-19. The NOEL for maternal toxicity was 740 mg/kg/day based on mortality, clinical observations and decreased body weight gain at 2,210 mg/kg/ day. The NOEL for developmental toxicity was 221 mg/kg/day based on increased post-implantation loss, decreased fetal weights and increased incidence of minor skeletal anomalies (retarded ossification) at 740 and/or 2,210 mg/kg/day (4).

In another developmental toxicity study, rabbits were administered propamocarb by gavage at dose levels of 0, 15, 45, 150, 300, or 600 mg/kg/day on gestation days 6-18. The NOEL for both maternal toxicity and developmental toxicity was 150 mg/kg/day, based on decreased maternal body weight gain and increased post- implantation loss at 300 mg/kg/day (4).

A three-generation reproduction study was conducted using rats fed a diet containing propamocarb at dietary concentrations of 0, 40, 200, and 1,000 ppm for 100 days and then continuously through 3 successive generations. No treatment- related effects were noted on either the parents or offspring (4).

Teratogenic Effects

Oral dosing of pregnant rats with 680 and 2040 mg/kg body weight of propamocarb hydrochloride was toxic to the dams and the conceptus. The NOEL was 204 mg propamocarb hydrochloride/kg body weight.

Oral dosing of pregnant rabbits with 280 mg/kg body weight of propamocarb hydrochloride was also toxic to the dams and the conceptus. The NOEL was 164 mg propamocarb hydrochloride/kg body weight (1).

Mutagenic Effects

No evidence of genotoxicity was observed in a battery of studies including Salmonella and E. coli gene mutation assays, 2 mouse micronucleus assays, an in vitro mammalian cytogenetic assay using cultured human lymphocytes, a yeast mitotic gene conversion assay and a yeast mitotic recombination assay (1, 4).

Carcinogenic Effects

In dietary rodent studies, propamocarb hydrochloride showed no evidence of carcinogenicity (1).

Organ Toxicity

No special studies have been conducted to investigate the potential of propamocarb to induce estrogenic or other endocrine effects. However, the standard battery of required toxicity studies has been completed. These studies include an evaluation of the potential effects on reproduction and development, and an evaluation of the pathology of the endocrine organs following repeated or long-term exposure. These studies are generally considered to be sufficient to detect any endocrine effects yet no such effects were detected. Thus, the potential for propamocarb to produce any significant endocrine effects is considered to be minimal (4).

Fate in Animals and Humans

Labelled material was administered orally to rats. Propamocarb hydrochloride is rapidly absorbed and almost totally excreted, predominately via the urine (>90% within 24 hours). Mineralization takes place via oxidation and hydrolytical decomposition (1).

ECOLOGICAL EFFECTS

Effects on Birds

The investigations on the acute and subacute toxicity of propamocarb hydrochloride gave the following values:

Acute toxicity (LD50 in mg/kg body weight): mallard duck >6289 mg/kg, pheasant 3050 mg/kg.

Subacute toxicity (5 day LC50 in mg/kg food): mallard duck 12,915 mg/kg, pheasant >25,000 mg/kg, Japanese quail >25,000 mg/kg.

Propamocarb hydrochloride can be classified as non-toxic to birds (1).

Effects on Aquatic Organisms

Fish. Acute toxicity studies fo the acive ingredient in various fish species gave the following LC50 values after 96 hours: mirror carp 235 mg/l, rainbow trout 410-616 mg/l, bluegill sunfish 415 mg/l.

Daphnia. Toxicological investigations of propamocarb on the water flea gave the following values: 48 hour EC50 of 295 mg/l, 48 hour No Observable Effect Concentration (NOEC) of 126 mg/l.

Algae. A laboratory investigation of the effects of propamocarb on green algae at 20C resulted in the following values: 96 hour EC50 of 350 mg/l, 96 hour NOEC of 22 mg/l.

It is concluded that propamocarb hydrochloride is of very low toxicity to aquatic organisms (1).

Effects on Other Animals (Nontarget Species)

Earthworms: The effects of propamocarb on earthworms were investigated using artificial substrate and the compost worm. The 14-day LC50 was >1000 mg/kg soil. Propamocarb can be classified as non-toxic to earthworms.

Bacteria: In a cell multiplication-inhibition test conducted on Pseudomonas putida, propamocarb only reduced cell multiplication at concentrations higher than 145 mg/l water. Consequently, propamocarb is only of very low toxicity to bacteria.

Soil micro-organisms: Investigations were conducted with propamocarb as 722 g/l aqueous solution at a concentration 10 times the commercially recommended dose rate. There were no adverse effects on dehydrogenase activity or nitrification (1).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Propamocarb hydrochloride does not persist in the soil. Following an adaption phase, it is rapidly decomposed by micro-organisms. The average half-life is less than 30 days; 90% of the original material is decomposed within less than 70 days.

The material does not leach and with the mineralization being so rapid, the compound does not contaminate the groundwater, even under favorable conditions (1).

Breakdown of Chemical in Surface Water

Propamocarb hydrochloride is very stable to hydrolysis and photolysis in sterile aqueous media. However, aquatic micro-organisms rapidly decompose propamocarb hydrochloride (up to 97% within 35 days). The material is also bound to the sediment, desorption is relatively weak (1).

Breakdown of Chemical in Vegetation

The metabolism of propamocarb hydrochloride was investigated using labelled material in tobacco, lettuce, cucumbers, potatoes, and ginger. The greatest part of the detected material was unchanged parent compound, with the other detected radioactivity coming from compounds produced by the plant by incorporation of labelled CO2 derived from soil-decomposed propamocarb hydrochloride (1).

Metabolism studies in potatoes, cucumbers and spinach demonstrated that propamocarb is degraded into carbon dioxide which is reincorporated into natural plant constituents. The primary residue found in all crops is the parent compound propamocarb hydrochloride (4).

Residue trials on potatoes indicated that residues of propamocarb in potatoes from foliar applications were below the Limit of Quatification (LOQ), at 2.5 times the maximum proposed label rate. No measurable residues of propamocarb were detected in any of of the processed commodities following treatment at 2.5 times the maximum proposed label rate and a shorter than proposed pre-harvest interval (4).

PHYSICAL PROPERTIES AND GUIDELINES

Technical propamocarb hydrochloride is crystalline and colorless. It is considered slightly corrosive to metals. It has a weak aromatic odor. The active substance is highly hygroscopic and therefore very difficult to handle (1, 3).

Exposure Guidelines:

LEL: 1000 ppm (33.3 mg/kg/day) Dog (4)
RfD: 0.11 mg/kg/day (4)

Physical Properties:

CAS #: 25606-41-1
Chemical name: Propyl [3-(dimethylamino)-propyl]carbamate-hydrochloride (1, 3)
Chemical Class/Use: carbamate compound used as a systemic soil and foliar fungicide for control of Oomycete diseases (5)
Solubility in water: 1005 g/L at pH 7 (3)
Solubility in other solvents: Soluble at 20[ring] C in acetone 560 g/L, methanol >500 g/L, isopropanol >300 g/L, ethyl acetate 23 g/L, hexane <0.1 g/L, and toluene <0.1 g/L (2)
Melting point: 45-55[ring] C
Vapor pressure: 8 x 10-4 Pa at 25[ring] C
Partition Coefficient (Kow): 0.84

BASIC MANUFACTURER

AgrEvo USA Co.
Little Falls Centre One
2711 Centerville Rd.
Wilmington, DE 19808
Telephone: 302-892-3000
Fax: 302-892-3013

Review by Basic Manufacturer:

Comments solicited: June, 1997
Comments received: July, 1997

REFERENCES

  1. Technical Information Bulletin for Propamocarb Hydrochloride. Fourth edition. 1995. Hoechst Schering AgrEvo GmbH. Berlin, Germany. 15 pp.
  2. New York State Section 18 Emergency Exemption for Propamocarb on Potatoes. 1996. Cornell University. Ithaca, NY 14853-0901.
  3. Farm Chemicals Handbook. 1997. Meister Publishing Co. Willoughby, OH 44094.
  4. U.S. Environmental Protection Agency. Pesticide Tolerance Petition for Propamocarb. Federal Register Document 97-5681. Tuesday, March 11, 1997.
  5. W.T. Thomson. 1997. Agricultural Chemicals. Book IV: Fungicides. 12th edition. Thomson Publications, Fresno, CA 93791.
  6. Review by Agrevo USA Company. July 21, 1997.